Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $207.72   12.558%   $233.8055   $233.81   $233.80   $233.80  
  Purchase #2 $236.61   10.626%   $261.7522   $261.75   $261.75   $261.80  
  Purchase #3 $106.94   12.182%   $119.9674   $119.97   $119.95   $120.00  
  Purchase #4 $85.44   12.582%   $96.1901   $96.19   $96.20   $96.20  
  Purchase #5 $223.92   6.251%   $237.9172   $237.92   $237.90   $237.90  
  Purchase #6 $199.78   11.324%   $222.4031   $222.40   $222.40   $222.40  
  Purchase #7 $164.54   10.630%   $182.0306   $182.03   $182.05   $182.00  
  7 purchase totals = $1,224.95       $1,354.0661   $1,354.07   $1,354.05   $1,354.10